cc: Partial draw without partial swap support.

cc/output/direct_renderer.h

Index: cc/output/direct_renderer.h
diff --git a/cc/output/direct_renderer.h b/cc/output/direct_renderer.h
index 864c1863b29db381bddfd83ded8ad054f23af6d1..70ae23f0a0a1e01606b1a7de2238f6907601d42a 100644
--- a/cc/output/direct_renderer.h
+++ b/cc/output/direct_renderer.h
@@ -182,10 +182,13 @@ class CC_EXPORT DirectRenderer {
   // This can be replaced by test implementations.
   std::unique_ptr<OverlayProcessor> overlay_processor_;
 
+  // Whether it's valid to draw with the current damage rect. Trivially
+  // true when using partial swap.
+  bool allow_partial_draw_ = false;
   // Whether it's valid to SwapBuffers with an empty rect. Trivially true when
   // using partial swap.
   bool allow_empty_swap_ = false;
-  // Whether partial swap can be used.
+  // Whether partial swap is used.
   bool use_partial_swap_ = false;
   // Whether overdraw feedback is enabled and can be used.
   bool overdraw_feedback_ = false;